1. Department of Microbial, Biochemical and Food Biotechnology, University of the Free State, P.O. Box 339, Bloemfontein 9301, South Africa.
2. Department of Plant Sciences, University of the Free State, P.O. Box 339, Bloemfontein 9301, South Africa.
3. Centre for Microscopy, University of the Free State, P.O. Box 339, Bloemfontein 9301, South Africa.